Question 23
The cells of a $10 \times 10$ square are susceptible to infection. In a unit of time, the cells with 2 or more infected neighbours (having a common side) become infected. Is it possible to start the infection in
a. nine cells,
b. ten cells,
in such a way that the infection spreads to the whole square?
a. nine cells,
b. ten cells,
in such a way that the infection spreads to the whole square?